1. Field of the Invention
The present invention relates to a multi-channel rotary joint for allowing flow along separate routes without allowing a plurality of fluids of the same or different types to be mixed between relative rotational members in a CMP (Chemical Mechanical Polishing) apparatus (an apparatus for surface polishing of semiconductor wafers) and the like.
2. Prior Art
In the surface polishing of a semiconductor wafer with a CMP apparatus, a turntable and a top ring are individually rotated with the semiconductor wafer sandwiched in between them. The supply of a wafer polishing liquid, wafer pressurized air, wafer cleaning water (pure water), air-blowing air, or the like, or the suction discharge of polishing residue, the vacuum chucking of a semiconductor wafer and a lapping plate or the like, and so forth may be performed between the rotating member (the top ring or the turntable) and the stationary side that supports the rotating member (the CMP apparatus housing). Accordingly, a plurality of fluid routes must be provided in between the rotating member and the stationary member in order to allow a plurality of fluids of the same or different types to flow, or to control these individually.
A rotary joint is generally used as the means for forming a series of fluid passages between relative rotational members.
In one proposed rotary joint for linking the stationary fluid passages formed in a stationary member such as the CMP apparatus housing to the rotating fluid passages formed in the rotating member such as the turntable or top ring, a joint housing attached to the stationary member is rotatably linked to a rotator attached to the rotating member, a first passage linked to the rotating fluid passages is forted in the rotator, a second passage linked to the stationary fluid passages is formed in the joint housing, and a stationary seal ring provided for a first passage opening of the rotator and a movable seal ring provided for a second passage opening of the joint housing rotationally slide over each other along with the rotation of the rotator produced by the rotating member, so that the first and second passages are rotatably connected in a sealed state by such two seal rings. More specifically, with a rotary joint as described above, the series of channels connecting the rotating fluid passages to the stationary fluid passages is made up of the center holes of the two seal rings and the first and second passages.
In the rotary joint structured as described above, however, the first and second passages are linked by the seal rings along the axis of the rotator, and a plurality of channels cannot be provided.
Consequently, the rotary joint described above cannot be used when a plurality of fluids of the same or different types are allowed to flow or controlled as discussed above, and applications of the joint is greatly limited. In such a situation, a plurality of rotary joints each having a single channel are generally combined, but such a structure considerably complicates the control system such as control valves and the flow routes, which makes the CMP apparatus more complicated and bulky.
Accordingly, it is an object of the present invention to provide a multi-channel rotary joint with which a plurality of fluids of the same or different types can be made to flow as desired between relative rotational members by means of separate routes without the fluids becoming admixed, and with which the flow conditions thereof (and particularly the pressure) can be controlled individually.
It is another object of the present invention to provide a multi-channel rotary joint with which the number of routes can be freely increased or decreased within the axial length of the rotary joint by varying the number of rows of mechanical and elastic seals, and with which a rotary joint with the required number of routes can be obtained with ease.
It is still another object of the present invention to provide a practical multi-channel rotary joint which can be used to advantage in various types of rotary devices that require separate flow and control of a plurality of fluids of the same or different types between relative rotational members, and which can be used in a wide range of applications.
The above objects are accomplished by a unique structure for a multi-channel rotary joint of the present invention that comprises: a joint housing; a rotator rotatably linked to the joint housing; a plurality of mechanical seals and at least one elastic seal disposed in a row in an axial direction of the rotator between opposing peripheral surfaces of the joint housing and the rotator; at least one first connecting space sealed by two adjacent mechanical seals and being an annular space formed between the opposing peripheral surfaces, and at least one second connecting space sealed by an elastic seal and a mechanical seal adjacent thereto; and a first fluid passage passing through the first connecting space, and a second fluid passage passing through the second connecting space, wherein
the mechanical seals are of end-contact types and equipped with: a stationary seal ring fixed to one of the opposing peripheral surfaces, a movable seal ring held axially slidable by another of the opposing peripheral surfaces, and a spring member that biases the movable seal ring to press against the stationary seal ring, the mechanical seals being of balanced types in which a balance ratio xcexa is 0xe2x89xa6xcexaxe2x89xa61, and
the elastic seal is equipped with: an annular main body and cylindrical inner and outer peripheral lips that protrude axially from the annular main body and are in elastically pressing contact with the opposing peripheral surfaces, the elastic seal being engaged and fixed to one of the opposing peripheral surfaces in a state in which an annular groove between inner and outer peripheral lips opens into a space with higher pressure out of the second connecting space and an adjacent space that is divided therefrom by the elastic seal.
In the above rotary joint, it is preferable for the elastic seals to be disposed on both sides of the mechanical seal group.
It is also preferable that the mechanical seal that seals at least one first connecting space be used also as a mechanical seal for sealing the first connecting space adjacent to the first connecting space.
The adjacent space divided from the second connecting space by the elastic seal includes, in addition to an atmospheric pressure space that communicates with or opens to the outside of the rotary joint, a second connecting space that is adjacent to the second connecting space. More specifically, when two second connecting spaces are provided adjacently with a single elastic seal in between, the adjacent space with respect to one of the second connecting spaces serves as the other second connecting space, and the elastic seal is disposed in a state in which the annular groove opens into the second connecting space with the higher pressure.
Also, the elastic seal is disposed in a state in which the annular groove opens into the higher pressure space, and this xe2x80x9chigher pressure spacexe2x80x9d is determined by the relative pressure relationship between the second connecting space and its adjacent space; and, except when the adjacent space is an atmospheric pressure space, is not determined by whether the pressure is higher or lower than atmospheric pressure, that is, by whether the pressure is positive or negative.